`string.partsn` and `string.partscn`

[LightAndLight]

string.partsn : Int -> String -> String -> { parts : Array String, rest : String }
string.partscn : Int -> Char -> String -> { parts : Array String, rest : String }

Like string.parts and string.partsc, but only get the first n parts,

[LightAndLight]

These seem very niche and I've forgotten what I wanted them for, so I'm doing to delay them until I find use cases.